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Solidifying memory while you sleep

Neuroscience professor Dr. Masami Tatsuno's investigations into REM and non-REM sleep and their effects on memory are producing findings that are quite awakening. Memory is a crucial brain function for humans and other animals; therefore, understanding how memory is encoded and maintained in the brain is an important problem of neuroscience.

Tatsuno, an AHFMR funded researcher at the U of L Canadian Centre for Behavioral Neuroscience (CCBN) and an iCORE scholar, is conducting studies aimed at understanding how REM and non-REM sleep contribute to memory consolidation. He investigates neuronal activity in lab animals to determine what types of memory benefit from REM and non-REM sleep, what the specific benefits are, and whether or not REM and non-REM sleep play complimentary roles in the formation of memory.

"Neuronal activity patterns that appear in the brain when a subject is engaged in a behavioural task reappear during the subsequent sleep," Tatsuno explains. "We call this memory reactivation or memory replay."

Many researchers believe that memory is stored on the connections between neurons. Changes in these connections due to some new experience or behaviour are reinforced again during sleep; this indicates the formation of new memory.

Tatsuno inserts multiple electrodes into the brains of his study subjects, monitoring up to 240 electrodes at a time to gain insights on how the brain functions and is subsequently modified during awake and sleeping conditions. Subjects are engaged in simple tasks such as running on a track or repeating a simple sequence. Tatsuno then investigates how the subjects' brains change by comparing neuronal activity during pre-task sleep, during the task, and again during post-task sleep.

Tatsuno has also been developing a computational technique that allows for the analysis of vast amounts of neuronal activity data. With his theoretical training in applied physics, he tries to integrate computational and experimental approaches in his research. The mathematics provides an insight into memory reactivation and learning, as well as the computational principles of memory function.

"Sleep is not only for recovery from fatigue; it plays an active and important role in memory formation," Tatsuno explains.